1. Field of the Invention
The present invention relates to an apparatus for rejecting containers which are being delivered by a conveyor, and more particularly to a container rejecting apparatus suitable for use with containers filled with a liquid such as beverage.
2. Description of the Related Art
There has been known a container rejecting apparatus having a pusher for rejecting containers filled with a liquid from a feed conveyor onto a discharge conveyor positioned adjacent to the feed conveyor. Containers that can be rejected by the container rejecting apparatus include PET (polyethylene terephthalate) bottles, glass bottles, cans, etc. The pusher is moved in a short stroke by an air cylinder to accelerate and push a container off the feed conveyor. The pusher moves in the short stroke because the pusher should not hit a next container when it moves back and forth. A flat plate of rubber or synthetic resin is attached to a front face of the pusher.
The feed conveyor comprises chains of synthetic resin and upper plates of synthetic resin which are integrally formed with the chains. The feed conveyor and the discharge conveyor move at the same speed. A guard rail is obliquely disposed over the discharge conveyor for preventing a rejected container from moving off the discharge conveyor. A container which has been pushed of f by the pusher moves obliquely forward at a constant posture onto the discharge conveyor due to inertia and friction with the discharge conveyor, obliquely hits the guard rail, changes its direction, and is finally discharged by the discharge conveyor.
As described above, the containers include PET bottles, and the PET bottles include those having a circular barrel and those having a rectangular barrel. The PET bottle have their bottoms whose central positions are raised into the bottles. Bottoms of various types of PET bottles which contact the conveyor are shown in FIGS. 7A, 7B and 7C of the accompanying drawings. That is, FIGS. 7A, 7B and 7C show the bottoms of various types of PET bottles, with contact areas between the bottoms and the conveyor being shown hatched.
FIG. 7A shows a circular PET bottle 1 which has a circular ring-shaped contact area 1a. FIG. 7B shows a circular PET bottle 1 which has a petaloid pattern of five contact areas 1b. FIG. 7C shows a square PET bottle 1 which has a square ring-shaped contact area 1c. The square PET bottles are conveyed by the feed conveyor while their sides are being parallel or perpendicular to the direction of movement of the feed conveyor.
In the conventional container rejecting apparatus, the distance between the front face of the pusher which is held in a standby position and the container that arrives at the position of the pusher is minimized to reduce a shock which is produced when the pusher hits the container. However, the container tends to fluctuate, i.e. be unsteady in its posture when it starts being moved because the container is abruptly accelerated by the pusher. It has been desired to prevent the container from fluctuating in its posture when it is pushed by the pusher and starts being moved.
In PET bottles, recently, small-size PET bottles having a volume of 500 ml have been used, and bottle filling lines have been operated at a high speed. Although a low-speed bottle filling line causes no problem, a high-speed bottle filling line requires the pusher of the container rejecting apparatus to be operated at a high speed. Thus, the PET bottles pushed by the pusher tend to fluctuate in their posture on their forward movement and fall down by contact with the guard rail. Those PET bottles which have a square ring-shaped contact area between the bottom and the conveyor are most liable to fall down, and those PET bottles which have a petaloid pattern of contact areas between the bottom and the conveyor are also liable to fall down. Those PET bottles which have a circular ring-shaped contact area between the bottom and the conveyor may fluctuate, but are less liable to fall down. It has been desired to be able to reject containers in a high-speed bottle filling line while preventing them from falling down.